Percutaneous ureteral occlusion with use of Gianturco coils and gelatin sponge. Part I. Swine model.

An animal model was developed to study ureteral occlusion produced by steel coils and gelatin sponge. A coil nest was formed in the ureter, and in all but one pig, gelatin sponge pledgets were incorporated in the coil nest. Animals were killed at 2 hours, 1 week, 1 month, and 2 months. High-grade obstruction was present immediately following the procedure in all animals and was documented to be persistent by means of antegrade nephrostograms obtained just prior to death. At gross examination after death, ureteral thickening and strictures were evident. Histologic studies helped confirm the presence of acute and chronic inflammatory changes. In the in vivo model, gelatin sponge was not found necessary for acute ureteral occlusion. However, in an ancillary in vitro study in which a rigid plastic tube was used, gelatin sponge was necessary in addition to coil occlusion to provide acute total obstruction. The authors' findings suggest that in a compliant ureter, coil occlusion alone produces sufficient mechanical occlusion. Long-term obstruction is probably due to mechanical obstruction and stricture formation.